DEPARTMENT  OF  COMMERCE  AND  LABOR 

BURKAU  OF  STANDARDS     ; 
S.  W.  STRATTON  .  .  Directoi 


THE  NATIONAL  BUREAU 
OF  STANDARDS 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1911 


DEPARTMENT  OF  COMMERCE  AND  LABOR 


BUREAU  OF  STANDARDS 
S.  W.  STRATTON  .  .  Director 


THE  NATIONAL  BUREAU 
OF  STANDARDS 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1911 


7/0  £3  660 


CONTENTS. 


Page. 

Introduction 5 

Length 7 

Mass 8 

Volume 8 

Density 9 

Trade  weights  and  measures 9 

Barometry 10 

Time 11 

Electricity 11 

Electrical  units  (international) 11 

Electric  resistance 12 

Electric  current 12 

Electromotive  force 12 

Absolute  electrical  units 12 

Electric  conductivity 13 

Electric  capacity  and  inductance 13 

Electric  instruments 14 

Magnetism 14 

Photometry 15 

Electrolysis 15 

Heat  and  thermometry 16 

Optics 18 

Chemistry 19 

Testing  materials 19 

Cement. 20 

Paper 20 

Textiles 21 

Miscellaneous  materials 21 

Engineering  instruments 22 

Engineering  testing 22 

Publications ; 23 

Equipment ._ 23 

(3) 


THE  NATIONAL  BUREAU  OF  STANDARDS.!  .  * 


INTRODUCTION. 

In  1901  the  National  Bureau  of  Standards  was  established  by 
Congress,  with  broad  functions,  consistent  with  the  modern  view 
of  standards  and  standard  measurements.  In  10  years  the  bureau 
has  grown  to  occupy  an  important  place  in  the  Government,  hav- 
ing 286  employees,  four  laboratory  buildings  in  Washington,  and 
branch  laboratories  in  Pittsburgh  and  Northampton,  Pa.,  and  in 
Charleston,  S.  C.  The  main  laboratories  are  located  in  the  north- 
western suburbs  of  Washington  at  an  elevation  of  350  feet  above 
the  Potomac  River,  on  a  natural  hill  site  of  about  8  acres — a  local- 
ity admirably  suited  to  its  work.  A  fifth  building  is  under  construc- 
tion for  the  electrical  work  of  the  bureau.  As  rapidly  as  consistent 
with  its  standard  of  work  the  bureau  has  taken  up  the  following 
functions  as  prescribed  in  its  organic  act: 

(1)  The  custody  of  the  standards,  which  involves  their  care  and 
preservation  and  also  the  intercomparisons  and  researches  necessary 
to  maintain  the  constancy  of  such  standards  as  are  liable  to  change. 

(2)  The  comparisons  of  standards  for  States,  municipalities,  in- 
stitutions, and  the  general  public — comprising  standards  used  in 
commerce,  manufacturing,  and  science,  assuring  to  the  public  accu- 
racy at  its  source — in  the  factory  and  the  works  laboratory. 

(3)  The  construction  of  standards  as  required  by  scientific  or 
technical  progress.     New  standards  are  constructed  at  the  bureau 
upon  the  basis  of  the  best  available  data,  in  some  cases  upon  re- 
searches at  the  bureau  and  sometimes  by  international  agreement. 

(4)  Standardization  of  measuring  apparatus  for  manufacturers 
as  a  test  of  their  output,  or  for  the  user  that  he  may  verify  instru- 
ments or  materials  independently. 

(5)  Technical  research  upon  problems  connected  with  standards, 
problems  arising  constantly  in  all  lines  of  testing  and  stardardiza- 
tion.     Such   research   facilitates   scientific   and   technical   progress, 
since  by  refined  measurements  alone  are  many  of  these  advances 
made  possible. 

(6)  Determination  of  physical  constants,  the  measured  data  re- 
lating to  materials  and  energy  which  underlie  scientific  and  tech- 

(5) 


6 

nical   work.    In  such  work  direct  reference  to   the   standards  is 
highly  desirable. 

(7)  Determination  of  the  properties  of  materials  for  general  use 
in  technology  and  trade.  This  work  is  based  upon  the  modern  view 
that  quality  depends  upon  definite  measurable  properties,  and  it 
therefore  requires  access  to  standard  measuring  apparatus  and  fa- 
cilities for  all  kinds  of  measurements. 

Weights  and  measures  were  once  restricted  to  length,  area,  volume, 
and  weight.  Within  recent  years,  however,  since  power,  electric  cur- 
rent, heat,  light,  irrigation,  refrigeration,  and  services  of  other  lands 
have  entered  the  world's  markets  as  commodities  for  production  and 
sale,  the  scope  of  weights  and  measures  has  broadened  to  include 
such  measures  as  those  of  velocity,  pressure,  energy,  electricity,  tem- 
perature, and  illumination.  The  importance  of  correct  standards 
and  uniformity  of  measures  is  readily  appreciated.  Almost  every 
industry  has  its  units,  its  particular  methods  of  measurement,  and  its 
special  measuring  instruments.  These  instruments  are  designed  for 
every  particular  need,  and  their  variety  is  evidence  of  the  high  state 
of  the  art  of  measurement  and  its  importance  in  industrial  and 
scientific  work.  Such  instruments  have  so  multiplied  and  the  demand 
has  grown  so  rapidly  that  the  manufacture  of  weights,  measures,  and 
measuring  instruments  now  forms  in  itself  a  whole  group  of  indus- 
tries. While  the  testing  of  standards  and  instruments  is  an  impor- 
tant part  of  the  bureau's  work,  not  less  important  is  the  research 
conducted  to  improve  standards  and  methods  of  measurement.  Hence 
it  is  necessary  to  maintain  a  force  of  men  and  an  equipment  for  doing 
scientific  work  of  the  highest  grade.  The  bureau,  as  a  court  of  highest 
appeal  in  matters  pertaining  to  measurement,  must  possess  standards 
as  perfect  as  possible.  Its  methods  and  instruments  must  be  the 
best  available,  its  laboratory  facilities  complete,  and,  finally,  men  of 
good  training  and  experience  must  be  in  charge  of  each  line  of  work. 

The  standards  of  the  bureau  are  made  available  for  the  service  of 
the  public  in  several  ways.  First,  the  States  of  the  Union  have  been 
furnished  by  the  Federal  Government  with  sets  of  the  metric  and 
customary  standards,  which  from  time  to  time  may  be  reverified. 
Standardizing  facilities  are  thus  afforded  for  local  inspection  of 
trade  measures.  Secondly,  tests  are  made  of  manufacturers'  stand- 
ards to  enable  them  to  maintain  a  high  standard  of  accuracy  in  their 
output.  Finally,  the  general  public  submits  to  the  bureau  stand- 
ards and  measuring  instruments  for  direct  test  at  nominal  fees.  The 
willing  cooperation  of  State  sealers  and  of  manufacturers  has  re- 
sulted in  a  steady,  and  in  some  cases  rapid,  improvement  in  indus- 
trial standards  and  products.  In  each  line  of  standardization  the 
cooperation  of  the  manufacturers  and  technical  experts  was  first  se- 
cured. Large  errors  were  often  found  in  the  products  submitted  for 


test  or  bought  in  the  open  market.  An  investigation  of  the  stand- 
ards used  by  manufacturers  showed  that  these  were  frequently  in 
error  by  amounts  that  could  by  no  means  be  neglected.  In  many 
such  cases  the  bureau  loaned  or  sold  standards  carefully  verified  by 
the  bureau,  and  the  ready  cooperation  of  the  manufacturers  greatly 
facilitated  the  work.  The  steady  improvement  in  the  measuring 
instruments  submitted  for  test  is  sufficient  evidence  of  the  effective- 
ness of  this  work.  Its  importance  to  industry  itself  and  to  the 
general  public  can  hardly  be  overestimated.  Directly  or  indirectly 
through  the  State  and  local  inspectors  and  the  manufacturers  the 
bureau  is  rapidly  bringing  about  a  realization  of  the  need  of  more 
perfect  standards  and  providing  means  by  which  they  may  be  applied 
to  all  the  varied  needs  of  industry,  science,  and  trade. 

The  bureau  is,  to  a  certain  extent,  a  clearing  house  for  technical 
information.  It  is  constantly  consulted  by  State  and  municipal 
officials,  and  technical  bodies  such  as  public-service  corporations  and 
commissions.  The  bureau  cooperates  to  the  fullest  extent  possible 
with  all  movements  tending  to  improve  conditions  in  which  stand- 
ards of  quality  or  standards  of  measurement  are  involved.  In  this 
way  the  bureau  is  influencing  in  a  far-reaching  way  the  establish- 
ment of  standardized  conditions  in  the  distribution  of  public  services 
as  well  as  promoting  accuracy  in  commercial  relations. 

LENGTH. 

To  meet  the  modern  demands  for  uniformity  and  precision,  all 
length  standards  are  based  upon  the  international  meter,  which  is 
defined  as  the  distance,  at  the  temperature  of  melting  ice,  between 
two  fine  lines  ruled  on  a  bar  of  platinum-iridium  preserved  at  the 
International  Bureau  of  Weights  and  Measures  near  Paris,  France. 
Accurate  copies  or  prototypes  have  been  made,  and  after  numerous 
comparisons  with  the  international  meter  and  among  themselves 
they  have  been  distributed  among  the  Governments  of  the  world. 
The  bureau  is  in  possession  of  national  prototype  No.  27.  From 
this  standard  are  derived  all  other  standards  of  length  used  in  the 
United  States,  with  their  subdivisions  and  multiples,  including  the 
yard,  using  the  relation  between  the  yard  and  the  meter  (1  meter = 
39.37  inches)  fixed  by  the  act  of  1866. 

Length  measures  are  standardized  under  definite  conditions  of 
temperature  and  manner  of  support.  The  tests  include  gauges,  bars, 
rules,  tapes,  level  rods,  and  a  great  variety  of  special  apparatus. 
The  researches  in  progress  relate  to  the  construction  and  mainte- 
nance of  standards  of  different  types  and  their  proper  use  and  care. 
Particular  attention  is  being  given  to  the  measurement  of  the  ex- 
pansion of  materials  at  high  temperatures  under  conditions  not 


8 

covered  by   ordinary   investigations  but  of   prime   importance   in 
modern  engineering. 

In  most  lines  of  construction  and  engineering  the  need  of  an  accu- 
rate standard  of  length  is  evident.  The  surveyor  or  engineer  re- 
quires steel  tapes  to  measure  distances  and  it  is  necessary  that  the 
true  length  be  known  in  terms  of  a  universal  standard  of  reference. 
The  unit  of  length  must  have  the  same  value  everywhere  to  secure 
perfect  construction  and  interchangeability  of  parts  in  machinery. 
This  can  only  be  done  by  having  accurate  and  universal  standards. 

MASS. 

To  secure  reliability  and  permanence  the  standard  of  mass  (com- 
monly called  weight)  is  a  certain  cylinder  of  platinum-iridium 
known  as  the  international  kilogram,  also  preserved  at  the  Interna- 
tional Bureau  of  Weights  and  Measures.  From  this  kilogram  copies 
have  been  made,  having  the  same  mass,  material,  and  form,  and 
after  careful  comparisons  to  establish  their  value  they  have  been 
distributed  among  the  various  nations  of  the  world.  The  bureau  is 
in  possession  of  two  such  copies,  Nos.  4  and  20.  From  the  kilogram 
all  other  units  of  mass,  such  as  the  pound  avoirdupois,  pound  Troy, 
etc.,  are  now  derived  in  the  United  States. 

Weights  are  classified  according  to  their  design  and  use,  and  are 
tested  in  conformity  with  the  classification.  The  weights  tested 
range  from  those  used  by  a  state  or  city  sealer  in  testing  commer- 
cial weights  and  measures  to  those  used  by  the  scientist  in  most  pre- 
cise and  exacting  work. 

Researches  made  from  time  to  time  cover  a  wide  field  affecting 
directly  and  indirectly  the  maintenance,  preservation,  and  proper 
use  of  standards  of  mass.  Millions  of  dollars  are  annually  involved 
in  the  tests  and  determinations,  made  by  engineers  and  chemists,  in 
which  weights  of  high  accuracy  must  be  used. 

VOLUME. 

Volume  measurements,  such  as  the  gallon  and  bushel,  are  defined 
as  a  certain  number  of  cubic  inches.  In  the  metric  system  the 
volume  occupied  by  a  kilogram  of  water  at  maximum  density  is  the 
liter. 

Tests  of  such  volumetric  apparatus  are  made  by  determining  the 
amount  of  distilled  water  at  a  certain  temperature  that  is  contained 
or  delivered  by  the  vessel.  The  tests  range  from  half-bushel  meas- 
ures to  cubic-centimeter  pipettes.  Each  year  many  thousand  glass 
measuring  instruments,  including  flasks,  pipettes,  burettes,  cylin- 
ders, and  vessels  of  all  kinds  are  tested.  The  test  of  cubic-foot 
standards,  used  in  standardizing  gas  and  water  meter  provers,  is  of 
growing  importance. 


Investigations  covering  questions  of  detail  and  design  are  impor- 
tant when  precise  volumetric  measurements  are  involved.  A  con- 
tainer made  of  1-liter  capacity  will  not  deliver  a  full  liter  of  a  liquid, 
and  it  is  necessary  to  have  precise  data  on  this  difference.  Precise 
volumetric  apparatus  is,  therefore,  marked  "to  contain"  or  "to 
deliver." 

The  glassware  tested  is  of  importance  to  chemists.  The  chemist 
in  making  analyses,  whether  of  the  constitution  of  rubber  or  steel  or 
of  a  sample  of  food,  needs  accurately  calibrated  glassware.  With 
the  advance  in  modern  requirements  the  testing  of  capacities  is 
steadily  assuming  greater  importance. 

DENSITY. 

In  a  large  class  of  materials  used  in  commerce,  science,  and  the 
arts,  it  is  important  to  determine  the  density  or  the  weight  of  a 
unit  volume  of  a  substance.  In  the  case  of  liquids  this  can  be  ac- 
complished with  a  high  degree  of  accuracy  by  hydrometers.  Hy- 
drometers are  usually  glass  bulbs  with  a  stem  which  when  placed 
in  a  liquid  sinks  to  a  certain  level,  indicating  the  density  by  gradua- 
tions on  the  stem. 

In  order  to  use  hydrometers  with  confidence  it  is  necessary  that 
they  be  carefully  tested.  The  bureau  tests  annually  hundreds  of 
hydrometers,  largely  for  the  use  of  the  revenue  service  of  the  Gov- 
ernment. Besides  testing  hydrometers,  the  bureau  is  called  upon  to 
make  careful  determinations  of  the  densities  of  materials,  in  both 
solid  and  liquid  forms,  of  special  interest  and  importance  to  revenue, 
commerce,  engineering,  and  science.  The  bureau  is  also  frequently 
called  upon  to  ascertain  the  expansion  of  various  liquids  upon  in- 
crease of  temperature. 

The  bureau  has  just  completed  an  elaborate  series  of  investiga- 
tions giving  probably  the  best-known  values  for  densities  of  mix- 
tures of  alcohol  and  water.  This  has  a  vital  bearing  on  the  work 
of  the  internal-revenue  branch  of  the  Government,  which  collects  the 
tax  on  malt  and  spirituous  liquors. 

Hydrometers  are  used  to  a  very  great  extent  in  the  petroleum  in- 
dustry and  by  manufacturing  chemists  and  in  tests  and  classifica- 
tions of  various  kinds.  The  importance  of  testing  h}^drometers  is 
better  appreciated  after  knowing  that  the  Government  collects  an 
annual  internal  revenue  of  $150,000,000  on  values  obtained  by  means 
of  hydrometers. 

TRADE  WEIGHTS  AND  MEASURES. 

The  Bureau  of  Standards  is  by  law  charged  with  the  preservation 
and  care  of  the  standard  weights  and  measures  of  the  National  Gov- 
ernment, and  soon  after  the  establishment  of  the  bureau,  in  1901,  it 
16313°— 11 2 


10 

began  to  receive  inquiries  from  State  and  private  institutions,  manu- 
facturers, and  from  the  general  public  for  information,  advice, 
and  assistance  concerning  weights  and  measures.  The  inquiries 
from  the  beginning  showed  the  great  variation  existing  in  the  dif- 
ferent States  and  the  lack  of  standardization  in  many  common  meas- 
ures of  quantity,  such  as  the  barrel  of  potatoes  or  apples  and  of 
boxes,  crates,  baskets  of  various  produce,  the  bushel  of  various  grains, 
etc.  Enormous  losses  to  the  public  naturally  result  from  such  a  con- 
dition of  affairs,  and  dishonest  dealers  take  advantage  of  these  condi- 
tions to  their  own  profit. 

Recognizing  the  benefits  which  would  come  from  unifying  the 
weights  and  measures  and  methods  in  use  throughout  the  country, 
Congress  made  an  appropriation  two  years  ago  to  enable  the  bureau 
to  make  an  investigation  of  the  actual  conditions  throughout  the 
States.  With  two  inspectors  engaged  in  this  work,  170  cities  in  46 
States  have  been  inspected.  More  than  8,700  scales  and  18,000  pieces 
of  other  weights  and  measures  apparatus  have  been  inspected.  The 
investigation  showed  that  a  large  number  of  fraudulent  or  defective 
weights  and  measures  are  in  daily  use. 

Through  the  information  thus  obtained  the  bureau  has  been  able 
to  point  out  existing  evils  and  to  aid  States  and  cities  in  drafting 
and  perfecting  their  ordinances  on  this  subject.  The  results  have 
been  gratifying.  During  the  past  year  12  States  have  enacted  laws 
which  will  result  in  State-wide  supervision  and  inspection  of  weights 
and  measures.  Seventeen  other  States  have  enacted  legislation  of 
a  minor  character — but  nevertheless  important — and  8  States  con- 
sidered legislation  which  failed  of  passage. 

It  is  the  hope  of  the  bureau  that  by  directing  and  encouraging  co- 
operation among  the  States  uniformity  will  be  secured,  and  that  the 
enormous  losses  now  sustained  by  the  purchasing  public,  whether 
through  dishonesty  or  carelessness,  will  be  reduced  to  a  minimum. 

BAROMETRY. 

The  needs  of  explorers  and  surveyors,  and  the  advent  of  the  mod- 
ern flying  machine,  have  emphasized  the  need  of  an  accurate  and 
ready  means  of  measuring  elevations.  This  has  directed  attention 
to  the  limitations  and  imperfections  of  the  aneroid  barometer,  used 
for  this  purpose.  The  bureau  is  investigating  the  behavior  of  such 
barometers  of  different  designs  under  various  conditions,  to  locate 
the  faults,  with  the  object  of  improving  the  instrument.  Standard 
specifications  and  tests  for  these  instruments  are  being  developed 
which  as  far  as  practicable  will  include  all  the  factors  affecting  the 
operation,  such  as  mechanical  accuracy,  elastic  lag,  temperature  com- 
pensation, permanency,  etc.  Mercurial  barometers  of  the  ordinary 
laboratory  type  and  those  used  for  meteorological  purposes  are  also 
tested  by  the  bureau. 


11 

TIME. 

The  bureau  is  preparing  to  take  up  the  testing  for  the  public  of 
the  better  grade  of  watches.  They  will  be  run  for  several  weeks  in 
the  various  positions  for  which  they  are  adjusted  in  a  room  heated  to 
summer  temperatures  and  again  cooled  to  nearly  freezing.  Any 
watch  passing  the  required  tests  will  be  granted  a  certificate  or  re- 
port of  its  performance.  Standards  of  accuracy  will  be  established 
which  will  indicate  the  degree  of  accuracy  which  may  be  expected 
from  watches  of  different  grades  and  enable  a  purchaser  to  secure  a 
certified  watch  if  he  so  desires.  Chronometers  and  clocks,  also,  will 
be  similarly  tested.  The  bureau  recently  completed  an  extended 
investigation  of  master  and  secondary  clocks  for  the  Treasury  De- 
partment, to  determine  their  suitability  for  installation  in  public 
buildings  of  the  Government. 

ELECTRICITY. 

The  accurate  measurement  of  the  various  electrical  quantities  oc- 
curring in  practice  is  of  great  commercial  and  technical  importance, 
as  well  as  of  scientific  interest.  The  bureau  is  responsible  for  the 
maintenance  of  the  units  in  terms  of  which  such  measurements  are 
made,  and  by  cooperation  with  other  national  laboratories  interna- 
tional uniformity  has  been  secured.  In  addition  to  this  work,  im- 
proved standards  and  measuring  apparatus  have  been  developed,  and 
in  some  cases  the  accuracy  of  measurement  greatly  increased.  The 
testing  and  certification  of  electric  instruments  for  all  who  employ 
them  in  their  work  is  also  an  important  function  of  the  bureau. 

INTERNATIONAL  ELECTRICAL  UNITS. 

The  units  to  which  electrical  measurements  are  referred  were 
adopted  by  the  London  International  Electrical  Conference  of  1908. 
The  fundamental  units  are  the  following:  (1)  The  international  ohm, 
defined  in  terms  of  the  resistance,  at  the  temperature  of  melting  ice, 
of  a  uniform  column  of  mercury  of  specified  dimensions;  and  (2) 
the  international  ampere,  the  unit  of  current,  defined  by  the  rate  at 
which  silver  is  deposited  by  an  electric  current  in  the  silver  volta- 
meter. 

The  completion  of  specifications  for  the  voltameter,  in  order  to 
assure  the  highest  accuracy  and  the  adoption  of  a  value  for  the 
Weston  normal  cell  used  in  practice  to  define  the  international  volt, 
was  left  to  an  international  committee,  under  the  auspices  of  which 
cooperative  work  was  carried  out  at  the  bureau  in  the  spring  of 
1910  by  representatives  of  the  national  laboratories  of  England, 
Germany,  France,  and  America. 

The  bureau  has  for  a  number  of  years  been  engaged  in  investiga- 
tions having  for  their  object  the  concrete  realization  of  the  funda- 
mental electrical  units  to  the  highest  degree  of  precision. 


12 

ELECTRIC  RESISTANCE. 

Four  copies  of  the  International  Ohm  have  been  constructed. 
This  involved  a  study  of  variations  in  cross-section  of  the  mercury 
column  due  to  minute  irregularities  in  the  capillary  tube  containing 
the  mercury,  the  accurate  determination  of  the  length  of  the  tube, 
its  mercury  content,  and  the  precision  comparisons  with  wire-re- 
sistance coils  employed  as  secondary  standards  for  routine  testing 
work.  The  resistance  units  represented  by  the  different  tubes  differ 
from  the  mean  of  all  by  only  5  parts  in  1,000,000,  and  the  mean  is 
in  agreement  with  the  units  employed  in  Germany  and  England  to 
a  very  few  parts  in  100,000. 

ELECTRIC  CURRENT. 

The  investigation  of  the  voltameter  has  shown  that  the  previously 
recognized  type  was  subject  to  large  errors  due  to  the  contamination 
of  the  electrolyte  by  the  filter  paper  employed  even  when  the  highest 
grade  paper  was  used.  When  the  latter  is  replaced  by  a  porous 
porcelain  pot  the  results  of  current  measurement  were  found  to 
agree  to  a  few  parts  in  100,000,  and  practically  the  same  result  is 
obtained  in  another  type  in  which  neither  filter  paper  nor  porous 
pot  is  employed.  The  investigation  brought  to  light  the  considerable 
influence  on  the  result  of  exceedingly  small  traces  of  certain  im- 
purities. The  experience  gained  will  be  utilized  in  drawing  up  the 
official  specifications  for  the  use  of  the  voltameter. 

ELECTROMOTIVE  FORCE. 

A  special  study  has  been  made  of  the  method  of  preparation  and 
purification  of  the  materials  employed  in  the  construction  of  the 
Weston  normal  cell,  which  is  in  practice  used  to  define  the  unit  of 
electromotive  force.  The  standard  cell  is  reproducible  to  a  few 
parts  in  100,000  if  the  cells  are  set  up  in  accordance  with  specifica- 
tions based  on  the  result  of  recent  investigations. 

ABSOLUTE  ELECTRICAL  UNITS. 

From  the  fundamental  electrical  units,  the  ohm  and  ampere  (or 
in  practice  the  ohm  and  volt) ,  all  the  remaining  units  for  the  meas- 
urement of  electrical  quantities  are  derivable. 

There  is,  however,  another  system  of  electrical  units  based  upon 
the  units  of  length,  mass,  and  time,  and  therefore  independent  of  the 
properties  of  materials.  These  units  are  called  absolute  units,  and 
upon  them  are  based  the  international  units  mentioned  above.  On 
account  of  the  scientific  and  theoretical  importance  of  the  subject 
the  bureau  has  been  engaged  in  the  development  of  a  current  balance, 
by  means  of  which  currents  can  be  measured  with  great  accuracy  in 
absolute  units.  This  involves  the  calculation  of  the  precise  attrac- 
tion or  repulsion  of  a  moving  coil  by  a  pair  of  fixed  coils,  all  the 


13 

coils  carrying  the  current  to  be  measured.  The  movable  coil  is  at- 
tached to  one  arm  of  a  balance  and  the  force  of  attraction  is  meas- 
ured by  weighing. 

The  results  obtained  with  the  current  balance  indicate  that  cur- 
rents can  be  measured  in  absolute  units  to  within  a  few  parts  in 
100,000  and  that  the  absolute  and  international  ampere  do  not  differ 
by  more  than  5  parts  in  100,000.  The  apparatus  for  the  determina- 
tion of  resistance  in  absolute  measure  has  been  constructed  and  the 
measurements  will  shortly  be  carried  out. 

CONDUCTIVITY, 

The  bureau  recently  made  an  investigation  of  the  conductivity  and 
temperature  coefficient  of  copper  used  in  such  enormous  quantities  by 
the  electrical  industries.  By  such  measurements  the  degree  of  purity 
of  a  copper  sample  may  be  ascertained,  certain  impurities  exerting  an 
influence  hundreds  of  times  greater  than  that  corresponding  to  the 
percentage  in  which  they  are  present.  The  results  obtained  were 
made  the  basis  of  the  new  copper  wire  tables  adopted  by  the  American 
Institute  of  Electrical  Engineers. 

CAPACITY  AND  INDUCTANCE. 

In  alternating  current  work  and  in  dealing  with  intermittent  or 
varying  currents  the  capacity  and  inductance  of  a  circuit  are  always 
of  importance.  This  applies  to  alternating  current  transmission  of 
power,  to  telegraphy,  submarine  cabling,  telephony,  and  radioteleg- 
raphy.  Indeed,  in  a  radiotelegraphic  circuit  where  the  changes  in 
the  current  are  very  rapid,  the  capacity  and  inductance  are  the  most 
important  constants  of  the  circuit. 

The  standards  of  capacity  are  mica  and  air  condensers,  the  mica 
condensers  being  used  for  values  of  the  capacity  greater  than  0.01 
microfarad,  and  the  air  condensers  for  lower  values.  Condensers  to 
be  tested  are  compared  with  these  standards  by  the  use  either  of  al- 
ternating or  direct  current,  according  to  the  purpose  for  which  the 
condensers  are  to  be  used.  Frequencies  of  alternating  current  from 
25  to  3,000  cycles  are  available  for  this  use. 

The  standards  of  inductance  are  coils  of  copper  wire  wound  on 
marble  spools,  which  are  nonmagnetic  and  very  permanent.  Stand- 
ards are  also  in  the  possession  of  the  bureau,  which  are  so  wound  that 
their  inductance  can  be  computed  from  their  dimensions. 

ELECTRIC  INSTRUMENTS. 

Another  branch  of  electrical  work  is  the  testing  of  the  electric 
measuring  instruments  largely  used  by  electrical  engineers.  This 
occupies  a  mid-position  between  the  work  of  an  engineering  labora- 
tory and  that  of  a  scientific  one.  An  important  part  of  the  work 
is  the  thorough  investigation  of  instrument  types. 


14 

Among  the  instruments  tested  and  certified  by  the  bureau  are 
resistance  standards,  precision  rheostats,  wheatstone  bridges,  poten- 
tiometers and  other  resistance  apparatus,  and  standard  cells,  all  of 
which  are  employed  in  scientific  work  and  in  the  more  accurate  meas- 
urement of  the  testing  laboratories  of  the  manufacturers  of  electrical 
apparatus,  and  of  the  light  and  power  companies. 

The  instruments  most  frequently  tested  are  ammeters,  voltmeters, 
wattmeters,  watt-hour  meters,  and  current  and  potential  transformers, 
although  many  other  types  are  often  tested.  The  reference  standards 
most  used  in  this  work  are  standard  cells  and  standard  resistances,  and 
the  potentiometer,  which  is  the  most  accurate  device  for  the  measure- 
ment of  voltage.  A  small  testing  room  has  been  installed,  the  tem- 
perature of  which  may  be  maintained  at  any  desired  value  between 
considerable  limits,  so  that  the  effect  of  temperature  upon  any  in- 
strument may  be  determined. 

The  watt-hour  meter  is  the  instrument  of  the  greatest  direct  com- 
mercial importance  since  it  is  almost  universally  used  wherever  elec- 
tric power  is  sold.  Instrument  transformers  are  used  as  auxiliary 
apparatus  in  the  measurement  of  very  large  amounts  of  power  in 
alternating-current  circuits. 

The  accuracy  required  in  all  such  measurements  is  steadily  increas- 
ing, and  consequently  instruments  are  being  developed  to  increase 
both  the  range  and  the  accuracy  of  such  measurements. 

MAGNETISM. 

Because  of  its  magnetic  properties  iron  enters  to  a  great  extent 
into  the  construction  of  electrical  machinery  and  apparatus.  Its 
value  consists  largely  in  its  intense  magnetization  when  it  is  sub- 
jected to  moderate  magnetizing  forces.  This  property  of  having  a 
high  magnetic  permeability  makes  it  useful  for  field  magnets  and 
armatures  in  a  great  variety  of  machines  and  apparatus  and  for 
alternating-current  transformers.  A  second  characteristic  is  the 
retention  of  a  certain  amount  of  magnetization  after  the  magnetizing 
force  has  been  removed.  This  property  is  valuable  in  steel  to  be 
used  for  permanent  magnets,  such  as  are  used  in  telephone  receivers, 
magnetos,  and  electric  measuring  instruments. 

The  measurements  of  the  above  characteristics  are  made  with 
direct  current,  and  are  known  as  normal-induction  and  hysteresis 
measurements. 

Besides  the  above  there  is  another  characteristic  of  iron  and  steel 
which  is  of  great  importance  for  material  to  be  used  in  armatures, 
transformers,  and  all  devices  in  which  there  is  a  repeated  reversal 
of  magnetization.  This  is  the  energy  loss  that  inevitably  results 
when  iron  or  steel  has  its  magnetization  reversed,  and  is  known  as 


15 

core  loss.  It  is  very  desirable  that  this  loss  be  kept  as  low  as  possible, 
It  has  been  estimated  that  in  the  United  States  alone  the  energy 
dissipated  in  core  losses  amounts  to  millions  of  dollars  annually. 
Recently  great  improvements  in  material  have  been  made,  and  the 
best  transformer  steels  of  to-day  show  only  half  the  loss  of  the  best 
material  of  a  decade  ago. 

Investigations  are  in  progress  to  show  the  relation  between  the 
magnetic  properties  and  the  chemical  composition  and  heat  treat- 
ment of  various  steels. 

Other  materials  besides  iron  and  iron  alloys  are  of  importance 
from  a  magnetic  standpoint.  For  certain  purposes  it  is  desirable 
to  have  as  nearly  nonmagnetic  materials  as  possible.  Some  alloys 
containing  a  considerable  percentage  of  iron  are  practically  non- 
magnetic, while  certain  alloys  of  nonmagnetic  metals  are  magnetic. 
An  investigation  of  such  slightly  magnetic  materials  is,  therefore, 
sometimes  of  importance. 

PHOTOMETRY. 

The  photometric  work  of  the  bureau  includes,  besides  research 
work  in  various  lines,  (1)  maintaining  the  unit  of  candlepower 
which,  at  the  proposal  of  the  bureau,  was  accepted  by  the  national 
laboratories  of  England  and  France,  and  is  preserved  through  the 
medium  of  incandescent  electric  lamps;  (2)  the  preparation  and 
testing  of  electric  lamps  to  be  used  as  photometric  standards;  (3) 
the  verification  of  gas  lamps  used  as  standards  in  the  photometric 
measurements  of  gas;  (4)  the  inspection  and  life  testing  of  incan- 
descent electric  lamps  purchased  by  the  Government  departments. 

The  adoption  of  the  new  candlepower  unit  of  the  bureau  by  both 
the  gas  and  electrical  industries  has  brought  about  uniformity  in 
the  photometric  standards  throughout  the  country. 

Standard  specifications  for  incandescent  lamps  issued  by  the 
bureau  are  recognized  by  all  manufacturers  and  have  brought 
about  a  uniformity  in  the  rating  of  lamps  which  is  very  much  to 
the  advantage  of  both  makers  and  users.  These  specifications  are 
frequently  revised  after  conference  between  representatives  of  the 
Government  and  of  the  manufacturers. 

Investigations  are  now  in  progress  to  determine  the  constancy  of 
incandescent  electric  lamps,  the  accuracy  of  photometric  measure- 
ments, and  the  reliability  of  flame  standards  employed  in  the  pho- 
tometry of  illuminating  gas. 

ELECTROLYSIS. 

Since  the  advent  of  trolley  systems  a  great  amount  of  damage  to 
gas  and  water  pipes  and  other  subsurface  structures  has  been  ex- 
perienced, due  to  the  presence  of  stray  currents  in  the  earth.  Vast 


16 

sums  are  spent  every  year  by  gas,  water,  and  railway  companies  and 
by  municipalities  in  efforts  to  mitigate  this  evil.  While  a  great 
deal  of  progress  has  been  made  in  methods  of  minimizing  trouble 
from  this  source,  much  remains  to  be  done  before  remedial  measures 
can  be  applied  with  the  degree  of  certainty  which  modern  engineer- 
ing practice  demands.  Closely  associated  with  electrolysis  from 
stray  currents  is  the  phenomenon  of  autoelectrolysis  or  self -corrosion, 
due  to  the  presence  in  the  soil  of  foreign  substances,  such  as  coal, 
coke,  cinders,  etc.,  which  give  a  difference  of  potential  against  iron, 
or  to  differences  in  the  physical  structure  of  the  iron  itself.  Corro- 
sion due  to  this  cause  is  often  difficult  if  not  impossible  to  distinguish 
clearly  from  that  due  to  stray  currents. 

During  the  last  few  years  much  attention  has  been  called  to  the 
possibility  of  damage  to  reenforced  concrete  by  stray  currents,  and 
considerable  alarm  has  been  aroused  in  some  quarters  lest  reinforced 
concrete  buildings,  bridges,  and  similar  structures  be  seriously  in- 
jured in  this  way.  Whether  or  not  such  grave  danger  actually  exists, 
the  possibility  of  such  danger  having  been  established,  the  problem 
becomes  one  of  extreme  importance,  and  a  thorough  study  of  the  con- 
ditions under  which  the  trouble  may  occur,  as  well  as  the  best 
methods  of  preventing  or  minimizing  the  trouble,  is  imperative. 
Recognizing  the  importance  of  the  subject,  and  acting  in  response  to 
important  engineering  interests,  the  Bureau  of  Standards  is  engaged 
in  a  comprehensive  investigation  of  this  subject,  involving  all  the 
different  phases  of  the  problem.  This  work  has  been  in  progress  for 
more  than  a  year  past,  and  several  papers  representing  the  results 
of  the  work  to  date  are  now  in  preparation.  It  is  planned  to  con- 
tinue this  work  as  circumstances  may  require. 

HEAT  AND  THERMOMETRY. 

The  work  of  the  bureau  in  connection  with  heat  measurements  is 
primarily  the  maintenance  of  a  standard  scale  of  temperature  always 
available  to  the  public  for  reference,  and,  secondarily,  the  making 
of  tests  and  the  investigation  of  problems  of  all  sorts  in  which  ac- 
curacy in  the  measurements  of  temperatures  is  essential  or  which 
for  other  reasons  may  advantageously  be  conducted  in  laboratories 
especially  equipped  for  experimental  work  in  heat. 

The  standard  scale  of  temperature  between  0°  and  100°  C.  (32° 
and  212°  F.)  is  represented  by  a  series  of  standard  mercurial  ther- 
mometers, which  agree  to  within  0?002  C.  with  those  which  define 
the  scale  of  the  International  Bureau  of  Weights  and  Measures. 
Above  and  below  this  range  the  scale  is  founded  on  a  number  of  fixed 
base  points  reproducible  by  the  boiling  or  freezing  points  of  chem- 
ically pure  substances.  The  value  of  these  base  points  are  expressed 


17 

in  terms  of  the  gas  scale.  Measurements  of  temperature  are  made 
by  thermometers  or  pyrometers  of  various  types  standardized  at 
these  base  points;  and  any  thermometer  or  pyrometer  sent  in  for 
test  is  standardized  in  terms  of  the  scale  of  the  bureau,  by  com- 
parison with  such  instruments,  or  by  test  at  the  base  points.  Among 
the  instruments  so  tested  the  following  classes  are  of  obvious  im- 
portance: Clinical  thermometers,  of  which  some  15,000  are  tested 
every  year;  calorimetric  thermometers,  used  in  determining  fuel 
values,  especially  in  connection  with  the  award  and  settlement  of 
coal  contracts ;  mercurial  thermometers,  for  use  in  controlling  various 
technical  operations  conducted  below  red  heat;  pyrometers  of  many 
kinds — resistance,  thermoelectric,  optical,  total  radiation,  etc. — which 
are  used  in  a  great  variety  of  technical  operations,  e.  g.,  in  the  glass, 
ceramic,  and  metallurgical  industries,  where  high  temperatures  must 
be  accurately  controlled. 

An  important  branch  of  work  directly  dependent  on  the  possession 
of  very  exact  means  for  measuring  temperatures  is  that  of  determin- 
ing the  specific  heats  and  heats  of  combustion  of  substances.  This 
includes  the  heats  of  combustion  of  certain  pure  gases  which  enter 
into  the  composition  of  illuminating  gas  and  certain  materials  capa- 
ble of  a  high  degree  of  purification,  such  as  sucrose,  naphthalene, 
and  benzoic  acid,  which  are  distributed  to  outside  fuel-testing  labora- 
tories for  use  in  standardizing  their  own  instruments. 

The  variety  of  miscellaneous  tests  on  the  thermal  properties  of 
materials  requested  from  the  bureau  is  very  large,  among  the  most 
important  being  tests  of  the  melting  points  of  fire  brick  and  other 
refractory  substances,  and  of  the  melting  or  transition  points  of  al- 
loys, in  connection  with  which  an  elaborate  investigation  of  the  effect 
of  heat  treatment  on  the  modern  steels  is  under  way. 

Besides  the  work  already  noted,  which  has  a  direct  connection  with 
the  improved  conduct  of  technical  operations  in  the  great  industries, 
various  researches  are  in  progress  tending  to  the  improvement  of 
methods  of  precise  measurement  in  the  domain  of  heat  or  of  our 
knowledge  of  important  thermal  constants.  Among  these  investi- 
gations may  be  mentioned:  Studies  of  freezing  and  boiling  points 
for  the  further  fixation  of  the  standard  scale  of  temperature;  the 
development  of  accurate  methods  of  calorimetry;  the  investigation, 
at  high  temperatures,  of  the  laws  of  radiation  on  which  the  indica- 
tions of  optical  and  other  radiation  pyrometers  depend,  and  of  the 
emissive  powers  of  various  materials  at  which  such  pyrometers  may 
be  sighted;  an  investigation  of  some  properties  of  the  thermometric 
gases  at  ordinary  and  low  temperatures;  a  comparison  of  various 
instruments  for  testing  the  viscosity  of  lubricating  oils,  etc. 


18 

OPTICS. 

The  work  in  optics  consists  chiefly  in  the  determination  of  the 
optical  properties  of  materials  and  optical  constants,  which  includes 
radiometry,  spectrometry,  polarimetry,  and  interferometry.  Such 
researches  are  valuable  in  supplementing  other  methods  used  for 
this  purpose.  Besides  the  researches  mentioned,  many  optical  tests 
are  made  for  the  Government  and  the  general  public,  such  as  tele- 
scopic and  photographic  lenses,  prisms,  samples  of  glass,  polariscopic 
apparatus,  and  sugar  analyses. 

In  interferometry  researches  have  been  completed  or  are  in  prog- 
ress on  the  use  of  spectrum  lines  and  their  application  to  the  most 
refined  methods  of  measurement  of  length. 

The  bureau  has  determined  the  purity  and  intensity  of  many 
sources  of  monochromatic  light,  the  relation  between  the  luminous 
intensity  and  energy  intensity  of  radiation,  the  radiation  of  conduct- 
ing helium  gas  as  a  primary  light  standard,  the  fidelity  of  photo- 
graphic lenses  as  to  reproduction,  the  luminous  equivalent  of  radia- 
tion, and  many  other  problems  of  a  similar  nature.  An  important 
investigation  recently  published  relates  to  the  luminous  equivalent 
of  radiation,  a  problem  which  underlies  the  theory  of  light  measure- 
ment and  the  establishment  of  a  rational  absolute  scale  of  luminous 
intensity.  A  method  has  also  been  developed  for  constructing  a 
rational  color  scale  and  establishing  primary  standards  of  pure  color. 
This  is  an  important  subject  and  one  which  has  many  industrial  and 
technical  applications. 

The  bureau  in  its  radiometric  work  investigates  various  problems 
in  light  and  heat  emission,  absorption,  and  reflection,  particularly 
in  the  infra-red.  It  has  studied  the  laws  of  radiation  of  various  sub- 
stances and  also  the  instruments  and  methods  used  in  such  researches. 
An  exact  determination  of  the  spectral  reflecting  power  of  metals 
has  also  been  published. 

Raw  sugars  that  are  imported  are  also  tested  to  determine  their 
purity,  which  it  is  necessary  to  know  in  order  to  fix  the  amount 
of  the  tariff  duty.  In  this  connection  samples  are  sent  in  daily  from 
the  various  customhouses  for  test.  Exhaustive  researches  are  also 
carried  on  to  improve  the  methods  and  instruments  used  for  test- 
ing at  the  ports  of  entry.  The  importance  of  applying  the  most  ac- 
curate and  scientific  methods  of  polarimetry  to  the  collection  of  the 
revenue  on  sugar  and  to  industrial  processes  is  increasing.  For 
this  purpose,  among  other  things,  pure  sugar  is  indispensable.  The 
problem  of  producing  relatively  large  quantities  of  this  material 
of  unexcelled  purity  has  been  successfully  solved  by  recrystalliza- 
tion  in  a  vacuum.  The  demand  on  the  bureau  for  samples  of  this 
sugar  is  rapidly  growing,  and  many  samples  are  now  sent  out  for 


19 

scientific  use.     The  distribution  of  such  samples  for  standardization 
marks  an  important  step  in  optical  measurements  and  calorimetry. 

CHEMISTRY. 

Broadly  speaking,  the  chemical  work  of  the  Bureau  of  Standards 
is  of  two  kinds,  routine  and  research,  done  independently  or  in  co- 
operation with  the  various  divisions  of  the  bureau.  By  far  the 
larger  part  of  the  routine  work  is  on  behalf  of  the  Government — 
analyses  of  iron,  steel,  alloys,  cement,  rubber,  oils,  paints,  varnishes, 
papers,  inks,  and  similar  miscellaneous  materials.  Most  of  this 
work  is  done  for  the  Isthmian  Canal  Commission,  the  Office  of  the 
Supervising  Architect  of  the  Treasury,  the  Government  Printing 
Office,  and  the  General  Supply  Committee  of  the  Government  de- 
partments at  Washington.  As  examples  of  research  work  on  behalf 
of  the  Government  may  be  mentioned  investigations  upon  cellu- 
loid and  articles  made  from  it,  with  reference  to  their  acceptance 
for  transportation  in  passenger  vessels  of  the  United  States;  print- 
ing and  record  inks,  with  a  view  to  improving  their  quality;  the 
celluloses  used  in  paper,  the  effect  of  age,  sizing,  etc.,  upon  them; 
the  preparation  of  the  purest  possible  ethyl  alcohol  to  serve  as  a 
basis  for  new  density  tables  for  mixtures  of  alcohol  and  water  for 
use  by  the  Internal  Eevenue  and  Customs  Services. 

TESTING  MATERIALS. 

An  important  branch  of  the  bureau's  work  relates  to  the  testing 
of  materials.  This  was  part  of  the  work  assigned  to  the  bureau 
by  act  of  Congress,  March  3,  1901,  by  which  the  bureau  was  estab- 
lished. The  development  of  the  work  was  taken  up  as  rapidly  as 
funds  were  provided  for  it  until  it  now  includes  a  large  variety  of 
structural,  engineering,  and  miscellaneous  materials.  The  impor- 
tance of  official  tests  of  materials  by  the  Bureau  of  Standards  arises 
from  the  fact  that  the  bureau  has  the  facilities  for  all  kinds  of  phys- 
ical measurements.  Among  the  more  important  materials  may  be 
mentioned  cements,  concretes,  steels,  irons,  bricks,  clays,  nonferrous 
metals,  alloys,  and  rubbers  for  various  purposes,  leathers,  papers, 
cloths,  inks,  paints,  mucilages,  twines,  ropes,  oils,  and  many  others. 
In  many  cases  satisfactory  methods  of  test  are  not  available,  and 
researches  are  necessary  to  devise  new  methods.  The  routine  tests 
of  such  materials  are  more  or  less  directly  concerned  with  every  de- 
partment and  bureau  in  the  Government  service  as  well  as  the  gen- 
eral public.  Equally  important  with  the  testing  is  the  study  of 
the  practical  and  scientific  basis  for  specifications,  the  desirable 
qualities  in  materials,  their  accurate  description  in  terms  of  phys- 
ical and  chemical  properties  which  may  be  measured  or  tested  by 
standard  tests  and  analyses,  standard  methods  of  sampling,  stand- 


20 

ard  instruments  and  methods  of  testing,  and  finally  the  preparation 
of  standard  specifications  for  the  guidance  of  the  manufacturer  and 
purchaser.  This  work  should  eventually  result  in  the  adoption  of 
definite  specifications  and  tests  for  all  materials  in  use  and  thus 
furnish  a  scientific  basis  for  manufacture  and  sale  and  a  reliable 
and  impersonal  standard  for  inspection  and  acceptance. 

CEMENT. 

In  connection  with  the  testing  of  structural  materials,  the  bureau 
is  conducting  several  cement-testing  laboratories  in  Washington, 
Pittsburgh,  and  elsewhere,  where  the  cement  used  in  the  construc- 
tion of  public  buildings  in  all  parts  of  the  United  States  is  tested. 
The  cement  used  in  the  construction  of  the  Panama  Canal  is  tested 
by  the  bureau  in  its  branch  laboratory  at  Northampton,  Pa.  The 
quantity  inspected  at  this  laboratory  averages  from  5,000  to  7,500 
barrels  per  day. 

In  addition  to  the  routine  testing  of  cement  various  problems  are 
being  investigated,  and  studies  are  being  made  in  an  endeavor  to 
improve  the  methods  of  testing.  A  small  cement  kiln  has  been 
installed  at  Pittsburgh  for  studying  problems  in  connection  with 
the  manufacture  of  cement,  varying  the  character  of  the  raw  ma- 
terials used,  temperature  of  burning,  etc.,  and  studying  the  effects 
of  these  variations  in  connection  with  physical  tests.  An  exposure 
station  has  recently  been  established  at  Charleston,  S.  C.,  for  con- 
tinuing the  investigation,  started  at  Atlantic  City,  as  to  the  effect 
of  sea  water  on  cements,  mortars,  and  concretes.  A  number  of 
technical  papers  giving  the  results  of  important  investigations  upon 
cement  and  concrete  are  now  in  press.  The  preparation  of  standard 
specifications  for  cement  is  now  in  progress  under  the  auspices  of 
the  Bureau  of  Standards,  to  fix  uniform  tests  and  requirements  for 
the  United  States. 

PAPER. 

Of  vital  importance  to  all  users  of  paper  is  the  bureau's  investi- 
gation and  testing  of  papers.  As  in  other  lines,  testing  and  research 
are  proceeding  together.  The  bureau  tests  all  the  papers  used  in  the 
publications  and  printing  of  the  National  Government.  Experts 
now  furnish  the  data  necessary  to  eliminate  undesirable  papers,  and 
quality  is  determined  by  scientific  tests  rather  than  by  inspectors1 
judgment.  As  a  result  of  the  movement  for  more  intelligent  buying, 
print  papers  are  bought  on  specifications  and  samples  of  all  deliv- 
eries are  analyzed  and  tested  at  the  bureau.  The  bureau  determines 
the  fiber  composition  by  the  microscope,  the  folding  endurance  by 
the  Schopper  folder,  the  weight  by  special  balances,  the  bursting 
strength  on  standard  paper  testers  carefully  calibrated  in  advance, 


21 

and  the  tensile  strength  and  thickness  by  special  devices.  After 
several  years  of  such  work  the  ground  is  prepared  for  a  thorough 
examination  into  the  factors  which  affect  the  qualities  of  paper. 
The  analyses  of  the  bureau  are  such  as  to  enable  the  expert  to  repro- 
duce the  formula  by  which  the  paper  was  made.  The  researches  in 
progress  include  the  effects  of  humidity  upon  the  properties  of  paper, 
such  as  strength,  weight,  thickness;  the  deterioration  of  paper  by 
coloring  matter,  loading,  sizing,  etc.,  and  the  study  of  the  dura- 
bility of  wood  cellulose  as  compared  with  cotton  and  linen.  The 
bureau  has  installed  a  paper-making  machine  for  producing  experi- 
mental papers  under  predetermined  conditions  and  of  definite  compo- 
sition. This  will  enable  the  bureau  to  investigate  the  properties  of 
paper  by  the  rigorous  control  of  the  conditions  of  its  production. 

TEXTILES. 

The  bureau  is  engaged  in  the  determination  of  the  physical  prop- 
erties of  textile  materials  from  the  raw  fiber  to  the  finished  product. 
These  tests  include  a  wide  range  of  measurement,  such  as  the  deter- 
mination of  the  absorption  of  moisture  by  wool,  cotton,  silk,  and  jute 
fiber  at  different  percentages  of  relative  humidity ;  the  shrinkages  of 
raw  wool ;  the  temperatures  to  be  applied  to  the  different  fibers  to  ob- 
tain constant  or  bone-dry  weight;  the  textile  strength  of  yarn  and 
other  fabric  as  affected  by  using  different  lengths  of  test  pieces ;  the 
effect  of  moisture  upon  the "  length,  strength,  weight,  durability, 
etc.,  of  textiles.  Textile  raw  materials  are  sold  by  weight,  and  the 
change  of  weight  due  to  the  absorption  from  the  air  is  therefore  a 
matter  of  commercial  importance.  Other  vital  problems  in  connec- 
tion with  textiles  are  in  progress,  in  which  the  Government  depart- 
ments, the  manufacturers,  and  dealers  have  expressed  a  keen  interest. 

MISCELLANEOUS  MATERIALS. 

Among  the  materials  tested  are  cast  iron,  steel,  and  other  metals, 
leather,  mechanical  rubber  goods,  asbestos  sheet  packing  and  other 
general  supplies.  The  metals  are  tested  for  strength  and  to  deter- 
mine compliance  with  specifications,  which  vary  according  to  the 
intended  use  of  the  material.  Finished  metal  products,  such  as  tools, 
saw  blades,  etc.,  are  tested  under  working  conditions,  the  tests  vary- 
ing with  the  uses,  frequently  involving  special  investigations. 

Leather  is  inspected  for  quality  and  tested  for  strength,  stretch, 
absorption,  and  weight,  to  determine  its  adaptability  for  special 
usage,  such  as  belting,  belt  lacing,  harness,  shoes,  and  other  products. 
Kubber,  in  the  form  of  mechanical  rubber  goods,  such  as  sheet  pack- 
ing, valves,  water  hose,  air  hose,  steam  hose,  suction  hose,  dredging 
sleeves,  rubber  belting,  etc.,  is  tested  for  strength,  elasticity,  and  gen- 


22 

eral  quality,  as  indicated  by  its  behavior  under  working  conditions, 
as  well  as  certain  special  tests  which  have  been  developed  for  such 
materials. 

Much  of  this  work  has  been  done  for  the  Isthmian  Canal  Commis- 
sion and  the  various  Government  departments,  with  the  result  that 
after  a  number  of  rejections  on  account  of  failure  to  comply  with 
specifications  it  is  now  found  that  such  materials  purchased  on  con- 
tract are  of  much  better  and  more  uniform  quality  than  it  was  pos- 
sible to  obtain  before  the  custom  of  testing  had  been  introduced.  The 
saving  in  expense  is  at  the  same  time  appreciable. 

Special  investigations  are  now  being  carried  on  to  determine  the 
physical  properties  of  various  rubber  compounds  which  are  used  in 
the  manufacture  of  mechanical  rubber  goods,  with  a  view  to  develop- 
ing standard  specifications  for  such  materials  as  hose,  packing,  etc. 
Similar  work  is  being  done  in  the  case  of  leather  belting. 

ENGINEERING  INSTRUMENTS. 

A  large  class  of  measuring  instruments  are  used  in  the  various 
branches  of  engineering.  The  investigation  and  testing  of  such 
instruments  is  an  important  part  of  the  bureau's  work,  comprising, 
among  others,  water-current  meters,  anemometers,  speedometers, 
taximeters,  tachometers,  pressure  gauges,  water  meters,  gas  meters, 
steam-engine  indicators.  These  instruments  are  tested  for  accuracy, 
and  certificates  issued  showing  corrections  where  desired. 

ENGINEERING  TESTING. 

The  work  of  testing  materials  requires  a  large  variety  of  testing 
instruments  and  other  equipment.  Among  these  may  be  mentioned 
the  2,300,000-pound  Emery  testing  machine  for  load  of  tension  and 
compression  to  accommodate  specimens  up  to  30  feet  in  length.  At 
its  Pittsburgh  laboratory  the  bureau  is  erecting  a  10,000,000-pound 
Olsen  testing  machine.  A  number  of  other  machines  of  smaller 
capacity  are  available  for  lower  ranges.  As  an  example  of  research 
with  such  testing  machines  may  be  mentioned  the  investigation  in 
conjunction  with  the  American  Society  of  Civil  Engineers  of  the 
strength  of  a  series  of  steel  columns  which  will  be  tested  to  correct 
and  confirm  the  formulas  used  by  engineers  for  computing  column 
strength — formulas  upon  which  the  efficiency  and  safety  of  building 
construction  depend. 

The  bureau  is  engaged  in  the  test  of  structures  in  which  strain 
measurements  are  taken  of  deformation  under  dead  loads.  This 
class  of  work  includes  civil  engineering  and  architectural  structures, 
embracing  bridges,  buildings,  railway  tracks,  steam  boilers,  and 
pavements.  Strain  measurements  are  carried  on  in  conjunction  with 


23 

laboratory  tests  of  the  physical  properties  of  the  different  materials 
represented  in  engineering  structures.  This  embraces  close  observa- 
tions on  the  behavior  of  the  materials  in  service,  supplementary  to 
but  beyond  the  scope  of  testing  machinery.  The  value  of  this  work 
lies  in  the  fact  that  it  is  directly  applicable  to  service  conditions  and 
is  made  upon  material  as  actually  used  in  finished  structures  and 
subject  to  working  conditions. 

This  work  is  the  summation  of  all  testing,  inasmuch  as  it  embraces 
all  the  factors  present  in  materials  in  structures.  The  work  has  in- 
clude^ measurement  during  construction  on  some  of  the  tallest  build- 
ings in  New  York  City. 

PUBLICATIONS. 

An  important  function  of  the  bureau  is  the  distribution  of  informa- 
tion. This  is  done  through  personal  visits  of  the  people  who  desire 
special  information,  such  as  manufacturers,  technical  experts,  and 
others  who  wish  to  consult  the  scientific  officers  of  the  bureau  regard- 
ing their  work  and  to  inspect  the  bureau's  plant  and  equipment. 
Such  information  is  also  largely  accomplished  by  means  of  corre- 
spondence, which  is  steadily  increasing  in  volume.  Finally  the  most 
important  medium  of  distribution  of  information  concerning  the 
bureau  and  its  work  is  through  its  publications.  The  Bulletin  of 
the  Bureau  of  Standards  embodies  the  results  of  the  scientific  work 
of  the  bureau  in  reference  to  standards,  instruments,  methods  of 
measurement,  and  physical  constants.  The  bulletin  contains  the  col- 
lected papers,  of  which  about  one  volume  is  issued  each  year.  The 
Circular  of  the  Bureau  of  Standards  contains  information  upon 
scientific  subjects,  including  methods  of  testing,  the  properties  of 
materials,  legislation  concerning  weights  and  measures,  regulations, 
specifications,  and  other  information  of  general  interest.  The  Tech- 
nologic Papers  of  the  Bureau  of  Standards  cover  the  more  strictly 
technologic  work  of  the  bureau.  The  separate  scientific  papers  are 
issued  in  the  form  of  reprints  for  general  distribution  upon  request. 
In  addition  to  the  above,  the  bureau  also  issues  miscellaneous  publi- 
cations, including  the  descriptive  pamphlet  of  the  metric  system, 
tables  of  equivalents,  reports  of  weights  and  measures  conferences, 
and  similar  material. 

EQUIPMENT. 

Besides  an  extensive  modern  equipment  of  scientific  instruments 
and  apparatus  for  experimental  and  testing  work,  the  general  equip- 
ment of  the  bureau  is  in  many  respects  unique,  since  the  range  of 
scientific  work  embraces  so  wide  a  variety  of  needs.  In  temperature 
work  ranges  must  be  available  from  that  of  liquid  air  to*  the  heat  of 
the  electric  arc;  in  electrical  work  all  varieties  and  the  maximum 
ranges  of  current  practicable  are  used;  in  chemical  work  the  usual 


24 

facilities  are  supplemented  by  many  special  services.  For  all  divi- 
sions of  the  work  are  available,  as  required,  electrical  power,  refrig- 
eration, steam,  gas,  compressed  air,  vacuum,  hot,  cold,  iced,  and 
distilled  water,  liquid  air,  cold  brine,  etc.  In  certain  classes  of  work 
temperature  control  is  required.  In  others  control  of  the  humidity 
is  needed,  e.  g.,  the  water  is  frozen  from  the  air  reducing  the  humidity 
to  the  desired  point,  while  in  others  the  humidity  is  varied  at  will. 
Similarly  other  conditions  are  controlled  to  secure  the  best  conditions 
for  effective  work. 

The  bureau  has  a  technical  library  of  more  than  8,000  bound 
volumes — chiefly  on  physics,  chemistry,  and  technology — and  regu- 
larly receives  270  journals  and  proceedings  of  scientific  and  technical 
societies.  Access  to  the  literature  in  any  subject  is  desirable  for 
effective  work,  especially  in  technical  investigations. 

The  character  and  quantity  of  the  results  attained  by  the  bureau 
have  largely  depended  upon  the  facilities  available  for  constructing 
special  apparatus  for  its  investigation  and  testing.  In  almost  every 
field  new  and  improved  apparatus  must  be  designed  and  constructed. 
The  bureau  is  therefore  provided  with  a  well-equipped  instrument 
shop,  skilled  mechanicians,  and  modern  machinery,  which  have  been 
an  important  factor  in  the  maintenance  of  a  high  standard  in  its 
technical  work. 


RETURN     Government  Documents  Department 

TO— *      350  Main  Library  642-2568 


LOAN  PERIOD  1 

2                               3 

4 

5                                6 

ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 

DUE  AS  STAMPED  BELOW 

NOV  2  4  1993 

UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
FORM  NO.  DD7.  68m.  1/82          BERKELEY,  CA  94720 


GENERAL  LIBRARY  -  U.C.  BERKELEY 


